Link adaptation technique is a technique aiming at overcoming a time-variation characteristic of a wireless channel and improving system performance. Its main advantage is capable of improving reliability of a communication link, increasing efficient use of power resources and frequency, and improving system quality of service and transmission capacity.
In LTE (Long Term Evolution, long term evolution) and subsequent evolution systems, AMC (Adaptive Modulation and Coding, adaptive modulation and coding) is a very important link adaptation method. However, measurement errors existing in actual system environment make the AMC unable to accurately track channel variation and acquire channel state, resulting in that a selected modulation and coding mode (which is usually represented by using MCS (Modulation and Coding Scheme, modulation and coding scheme) value) is not matched with the actual channel transmission environment. When the selected MCS value is lower than a channel-tolerable MCS value (defined as an MCS value when a channel sends information to the utmost), it indicates that channel resources are not fully utilized; whereas when the selected MCS value is higher than the channel-tolerable MCS value, the probability of transmission errors will be increased, resulting in a retransmission, which causes a waste of system power and frequency resources.
Regarding this problem, currently, a technique—OLLA (Open Loop Link Adaptation, open loop link adaptation) is used, wherein a reasonable correction is performed to the MCS value selected by the AMC based on HARQ (Hybrid Automatic Repeat Request, hybrid automatic repeat request) information fed back by a user equipment, system measurement errors will result in an error between the MCS value used in the AMC and the channel-tolerable MCS value, the error can be adjusted by setting a correction amount, and the size of the correction amount is referred to as an OLLA value. During the transmission process, the system will continually adjust the OLLA value. However, the prior art does not distinguish different states of the user equipment when the OLLA value is adjusted, so that the OLLA value corresponding to the MCS value during information transmission process of the user equipment in different states cannot be acquired efficiently, resulting in a relatively large error in the OLLA value corresponding to the MCS value acquired by the system, and affecting transmission performance of the system.